Control systems are used in controlling actuators that position read/write heads over selected tracks of a disc drive, as well as in other applications. When the actuator's gain or other characteristics are non-linear due to end effects or leakage flux, or vary undesirably with temperature or some other environmental condition, then a controller will often be used that adapts its controller parameters in real time to compensate for the uncertain variations. Such “adaptive controllers” are typically realized as discrete (digital) controllers. The controllers are often complex and require that complex and lengthy calculations be completed in a very short time in order to achieve rapid actuator movements with short settling times and stability over the entire operating range. In particular, with the use of newer high density recording media in disc drives, improved controller performance is needed to meet more stringent positioning and speed requirements. Completing the lengthy and complex calculations in a short time requires high memory use and high clock speeds leading to undesirable high power consumption and heating in the controller. An adaptive controller for an actuator is desired that has reduced computational overhead and reduced power consumption, while achieving rapid, precise and stable control of the actuator.